The present invention relates to a binocular indirect ophthalmoscope and to a laser accessory therefor.
Ophthalmologists need to examine the retina for a number of reasons. An indirect ophthalmoscope is one of a number of devices used for this purpose. An indirect ophthalmoscope is, typically in essence, a pair of viewing binoculars, for example with 2xc3x97 magnification, mounted on a headband with an integrated light source for projecting light into the patient""s eye to enable the retina to be viewed by a clinician wearing the ophthalmoscope.
It is known to integrate a laser into the headset of the ophthalmoscope in order to treat disorders observed by the clinician, for example by a photocoagulation treatment of a peripheral portion of a patient""s fundus oculi. 
The design of an attachment for providing a laser beam, conventionally involves an optical fibre delivery system for connection to the laser and an associated set of optical elements for focussing the divergent beam from the fibre""s distal end to the patient""s eye. These may include, dependent on design, a lens for converging the laser beam and possibly a mirror for deflecting the beam out to the patient at a distance of approximately 30 centimetres in front of the ophthalmoscope.
Whatever the delivery method, the output elements of the laser delivery system need to be secured in front of the ophthalmoscope.
Hitherto no one has been able to mount the laser delivery coaxial with the viewing path due to the mechanics of the laser delivery. Having the laser coaxial with the vision is the ideal scenario for the surgeon.
The final deflecting mirror or lens has always been mounted above or below the line if sight in order to preclude obstruction of the surgeons view. The beam therefore converges into the eye at an angle rather than being in the visual plane of the ophthalmoscope.
The mounting of the output optics in front of the ophthalmoscope has been a major problem as the goal is to achieve coaxiality with the vision.
Introducing the laser from above the line of sight of the ophthalmoscope at 12 o""clock necessitates having a mirror angled at 45 degrees to the vertical plane. This is secured on a shaft in the opposite plane if movement of this mirror is to be achieved. A rotatable shaft with a cam mechanism is often employed to tilt the mirror to the required position. This shaft would obscure the vision of the ophthalmoscope if it were in the plane of his line of sight. This alone necessitates the mirror assembly to be mounted above or below the line of vision.
It is possible that if the line of vision is directed through the centre of a patient""s pupil, the laser-beam, which is angled to the line of vision, may clip the patient""s iris.
This is a common problem and clinicians use eye drops in order to dilate the pupil as much as possible in order to reduce this disadvantage. Unfortunately diabetics have glycogen disorders within the iris structure and dilation is not always possible which hinders further the procedure. If the laser beam were coaxial with the viewing optics the problem would be greatly alleviated.
Accordingly known laser beams projected from the ophthalmoscope are not parallel with the optical axes of the binocular. They converge at an angle of about 5 to 10 degrees.
It is a principal object of this invention to provide an alternative laser delivery means for an indirect ophthalmoscope.
According to a first aspect the invention comprises a binocular indirect laser ophthalmoscope comprising binocular eyepieces each having an optical axis defining an optical plane, the ophthalmoscope having a central viewing axis lying in said optical plane; and an optical element adapted to position a laser beam into said optical plane substantially on said viewing axis and substantially parallel to said viewing axis.
According to a second aspect the invention comprises a laser-directing attachment for attaching to an indirect ophthalmoscope comprising: an attachment mechanism adapted to attach said attachment to the ophthalmoscope; a laser fibre connector adapted to connect to an optical fibre adapted to carry a laser beam; a director adapted to direct a laser beam in a direction relative to said attachment; and direction controls adapted to control the director to place a laser beam emitted via said connector in a line generally superimposed upon a central viewing axis of said indirect ophthalmoscope.
According to another aspect of the invention a binocular laser indirect ophthalmoscope comprises: a pair of eyepieces for a user to look through, and respective image capture optics associated with respective eyepieces, said eyepieces and associated image capture optics having respective optical axes, said optical axes defining an optical plane, and there being a central line of view of said ophthalmoscope lying in said optical plane; a laser beam coupler for coupling a laser beam delivery device to said ophthalmoscope; a laser beam director for directing a laser beam provided from said laser beam coupler forwards, away from said ophthalmoscope; an adjustment mechanism for controlling the position or orientation of said laser beam director so as to vary the position or direction of a laser beam propagating from said director; and wherein said laser beam coupler is provided disposed laterally to one side of said image capture optics and said laser beam director is provided in front of said image capture optics, and wherein said adjustment mechanism is adjustable to position a laser beam propagating from said director substantially in said optical plane of view, substantially undivergent therefrom and substantially on said central line of view.
According to another aspect the invention comprises a device for attachment to an indirect ophthalmoscope for fitting a laser to said ophthalmoscope, said device comprising: a support member; an attachment formation provided associated with said support member for attaching said support member to said ophthalmoscope; a laser director coupled to said support member by a mechanical coupling mechanism so as to be movable relative to said support member;, a control mechanism for moving said laser director relative to said support member; wherein said device has a forward-facing front portion away from which a laser beam is directed in use, and a rearward facing pack portion which in use is disposed towards an operator""s face, and a side portion laterally disposed to one side of said device; and wherein said mechanical coupling mechanism is provided at said side portion.
According to another aspect the invention comprises a method of aligning a laser beam of an indirect binocular laser ophthalmoscope with a visual plane of said ophthalmoscope defined by first and second optical axes of first and second eyepiece optics of said binocular ophthalmoscope, said method comprising providing a reflector between said optical axes such that said reflector intersects said visual plane; directing a laser beam onto said reflector at about the position where said reflector intersects said visual plane; and controlling the orientation or position of said reflector so as to cause a laser beam reflected from said reflector to be in or parallel to said visual plane.
Preferably the binocular ophthalmoscope has a central viewing axis and the method comprises emitting the laser beam generally on the viewing axis.
According to another aspect the invention comprises a method of aligning a laser beam of an indirect binocular laser ophthalmoscope with a visual plane of said ophthalmoscope defined by first and second optical axes of first and second eyepiece optics of said binocular ophthalmoscope, said method comprising providing a beam manipulator between said optical axis, such that said beam manipulator intersects said visual plane, and causing said laser beam to enter said ophthalmoscope laterally to one side thereof.
According to another aspect the invention comprises a method of laser treatment of an eye by controlling the position at which a laser beam encounters a structure of said eye by using an indirect ophthalmoscope having a laser director optical element, by providing said laser beam from the side of said ophthalmoscope and providing said optical element substantially in a vertical plane inclined at about 45xc2x0 to a line of propagation of said laser beam, thereby directing said laser beam away from said ophthalmoscope substantially in and parallel to a plane defined by optical axes of binocular optics of said ophthalmoscope.
According to another aspect the invention comprises a method of laser treatment of an eye comprising controlling the position at which a laser beam encounters a structure of said eye by using an indirect ophthalmoscope having a laser director optical element provided in a frame, the user looking through said frame at the eye to be treated; bodily moving said frame so as to move the path of said laser beam to lie in or parallel to a visual plane defined by optical axes of the binocular optics of said binocular ophthalmoscope; and activating said laser beam.
According to another aspect the invention comprises a method of controlling the angle of a laser beam relative to a viewing plane of a binocular laser ophthalmoscope, said viewing plane being defined by first and second optical axes of respective first and second optical pathways of said binocular ophthalmoscope, said method comprising providing an optical element on a carrier mounted on said ophthalmoscope; looking through said carrier; moving said carrier relative to other parts of said ophthalmoscope so as to move said optical element thereby altering the angle at which said laser beam will propagate relative to said visual plane.
According to another aspect of the invention a binocular indirect ophthalmoscope has first and second image capture optics having respective first and second optical pathways which define a viewing plane, and delivery means for delivering a laser beam to an optical element located adjacent said image capture optics for causing said laser beam to be emitted in a direction substantially in said viewing plane, undivergent therefrom.
According to another aspect the invention comprises a binocular indirect ophthalmoscope having a central viewing axis lying in a viewing plane which contains the optical axes of the binocular optics, and means for delivering a laser beam in that plane to an optical element for deflecting said laser beam to a direction substantially on and parallel to said viewing axis.
According to another aspect the invention comprises a binocular indirect ophthalmoscope whose eyepieces have optical axes which define a viewing plane, a mirror carrier frame which has a viewing opening or window registered with said eyepieces and has a dichroic mirror mounted in that viewing plane extending across said viewing opening, and delivery means for delivering a laser beam to said mirror for reflection into said viewing plane and along a central viewing axis of said ophthalmoscope.
According to another aspect the invention comprises an accessory for a binocular indirect ophthalmoscope which comprises a frame having viewing openings located to either side of a reflective surface, and directing means for directing a laser beam onto said reflective surface for reflection into a viewing direction.
According to another aspect the invention comprises an accessory for a binocular indirect ophthalmoscope which comprises a frame having a viewing aperture and an optical element disposed across said viewing aperture, said optical element being adapted to reflect light of a selected laser wavelength and transmit light of at least another selected optical wavelength such that in use a user is able to look through said viewing aperture and through said optical element.
Said reflecting surface, or other optical element, may be mounted as a central bridge piece of a cage or carrier which defines viewing openings in register with each said eyepiece and to each side of the reflective surface (or optical element). Alternatively, said reflecting surface, or other optical element may be disposed in front of said viewing aperture/openings and the user may look through said optical element.
The cage or carrier is preferably adjustable in angle about an axis which lies in, or is parallel with, the said viewing plane and which is substantially normal to said central viewing axis.
In an embodiment of the invention the laser beam is delivered substantially normal to said line of sight and is reflected onto the line of sight by a mirror mounted to said cage. This allows an optical fibre infeed to be brought down from overhead. This is an arrangement which is more convenient for the user.
The means for delivering the laser beam is preferably arranged also to deliver an aiming beam of a visible light, e.g. from a diode. Such a visible light beam may be used as an aiming marker for any laser treatment to be carried out.
Any suitable laser may be used.
The apparatus preferably includes dichroic filters which are interposed between the laser light path and eyepieces of the binocular. This will protect the eyes of the clinician from any laser light reflected back from the eye of the patient.